This is a very interesting thread. I'd like to make a few comments based on being an avid reader and having a service facility about 5 miles from the Chevron research center for many years. There is also a large Ortho research center next to it. Through the years some of the chemical engineers were my customers. I particularly remember one gentleman by the name of Heinz Webber. Boy, don't try to tell him anything about gasoline. These gentlemen were always willing to answer my questions.

Lead was used to protect valve seats. This protection was needed in engines that didn't have seats that could handle the heat. As someone pointed out you don't need the protection for around town driving. The lead stayed on the seats for awhile even after switching to unleaded.

When the lead was taken out of fuel you could legally buy phosphate based additive, but it had to be added with every tank. I'm assuming it is still available for older cars that haven't been upgraded.

Also in the interest of the environment, all aromatic hydrocarbons were removed. All truckers can tell you exactly when that happened. Three things happened when these were removed. Octane rating went down in gasoline. Cetane rating went up in diesel. All the worn seals that weren't made of viton in diesel injection pumps shrank and allowed them to leak. All these seals would have leaked earlier in life if they hadn't remained swollen in the presence of aromatic hydrocarbons.If you want to boost your octane or stop an old diesel pump from leaking, go down to your chemical supply house and buy a gallon of technical grade zylene. You will have to fill out a form saying you won't make bombs or dope and give them about ten bucks.

Lead is not only a health hazard, it fouled plugs and carboned up the engine. The removal of lead from fuel is why we have all these new split fire and multi electrode spark plugs on the market today. In the old days plug manufacturers sold their plugs at cost to the engine assy plants, because there was a very good chance the consumer would request that brand in 10,000 miles for the tuneup. There is where the money was made. Now with 50,000 mile plugs, sans the lead and people keeping cars longer, that link is gone. So now plug makers have convince buyer that their newest multi electrode plug is far superior to what the competition has.

We are so used to the exhaust of the modern cleaner burning engines that we need to be reminded once in awile when we are standing next to an oldie from the 50s or 60s. My eyes start wattering, not so much from nastalgia, as from the fumes that are burning my eyes.